Field of Technology
The present disclosure relates to an in-cell touch display device.
Discussion of the Related Art
In an information-oriented society, technology relevant to the field of display devices for displaying visual information as an image or a picture is being developed. Particularly, there are touch display devices each including a display panel which senses a touched position and a touch force when a user contacts a display area displaying an image or applies a force to the display area with a finger, a pen, or the like. The touch display devices are being widely applied to smartphones, automated teller machines (ATMs), ticket vending machines, exhibitions, etc. for immediate and mutual communication between a user and a machine.
Each touch display device includes a display panel which displays an image and senses a touch, a panel driver for driving the display panel, and a timing controller that supplies a signal for controlling the panel driver. The panel driver includes a gate driver, which supplies a gate signal to a plurality of pixels, and a data driver that supplies data voltages to the pixels. The data driver includes a plurality of source drive integrated circuits (ICs).
A display device where a display panel for displaying an image and a touch panel for sensing a touch are individually provided is defined as an on-cell touch display device. On the other hand, a display device where a display panel for displaying an image supplies touch sensing-enabled information to a touch driver is defined as an in-cell touch display device. The in-cell touch display device does not include a separate touch panel, thereby decreasing a thickness of the touch display device.
The in-cell touch display device includes elements for sensing a user touch applied to a display area. Therefore, the in-cell touch display device has a display period where an image is displayed and a touch period where a touch is sensed. During the touch period, the display panel is supplied with a common voltage Vcom for sensing a touch.
A direct current (DC) voltage electric field (DC field) based on the common voltage is generated in an outer area of the display area. A black matrix (BM) which divides the pixels in order for light emitted from the pixels not to be mixed with one another is provided on an upper substrate of the display panel. A general resin BM is a BM formed of a resin having a resistance which is 106Ω/D or less per unit length. The general resin BM is relatively low in resistance, and thus, disperses electric charges well. Therefore, in a case using the general resin BM, a DC accumulation amount based on the DC voltage electric field is small.
However, the general resin BM prevents a capacitance from being generated between a touch electrode and a finger due to a touch by a finger or the like. A capacitance is generated between the general resin BM and a finger. Therefore, in a case where the general resin BM is applied to the in-cell touch display device, touch performance is reduced. Therefore, among resin BMs, a high-resistance BM formed of a resin having a resistance which is 1010Ω/D or more per unit length should be used for enhancing a touch performance of the in-cell touch display device.
When the DC voltage electric field is generated for a long time, the high resistance of the high-resistance BM makes it difficult to disperse electric charges. For this reason, DC accumulation is caused by the DC voltage electric field. In the in-cell touch display device including the high-resistance BM which is high in DC accumulation amount, adsorption of a pollution component occurs frequently.